In the building industry, it is often necessary to raise a building, e.g. to raise a riverside or seafront building above flood or high-tide level. A typical example of this is the city of Venice, where the ground floors of buildings are regularly flooded by so-called “high-water phenomena”.
Alternatively, a building may be raised to build a basement underneath, in situations in which excavating underneath the building is undesirable or impossible, or to increase the height, to make full use, of a floor.
Patent IT1303956B proposes a method of raising a building, whereby a new foundation is built comprising a number of through holes; and, for each through hole, a connecting member fixed to the foundation, adjacent to the hole, and projecting at least partly upwards; a pile is then inserted through each hole, and a first thrust is applied statically to the pile to drive it into the ground (the first thrust is applied by a thrust device located over the pile, cooperating with the top end of the pile, and connected to the projecting part of the connecting member, which, when driving the pile, acts as a reaction member for the thrust device). Once all the piles are driven into the ground, a second thrust is applied statically between each pile and the foundation to raise the building with respect to the ground; and, once the building is raised, each pile if fixed axially to the foundation.
Patent Application WO2006016277A1 proposes a method of raising a building resting on a supporting body in turn resting on the ground, whereby a new foundation is built comprising a number of through holes; and a number of connecting members, each fixed to the foundation, close to a hole. A pile is then inserted through each hole, with its bottom end resting on the supporting body, and its top end projecting from the hole; each pile is then fitted with a thrust device, which rests on the top end of the pile on one side, and is connected to the corresponding connecting member on the other side; and, finally, thrust is applied statically to each pile by the thrust device to raise the building with respect to the supporting body. Once the building is raised, each pile is fixed axially to the foundation. The difference between the lifting methods proposed in Patent IT1303956B and Patent Application WO2006016277A1 substantially lies in the fact that, in Patent IT1303956B, each pile is driven individually into the ground before commencing the lifting operation, whereas, in Patent Application WO2006016277A1, a supporting body already exists between the building and the ground, so the building is raised without driving the piles into the ground first.
In the case of a very large building and/or unusual structural situations, the above known methods leave room for improvement, in that, at the actual lifting stage, the building structure has been found to potentially undergo severe stress requiring major consolidation work.